Reflector, liquid crystal display device having reflector, method of manufacturing reflector, and method of manufacturnig liquid crystal display device

ABSTRACT

A reflector for reflecting incident light from outside includes an insulating film being formed on a substrate and including multiple concavities and convexities, and a metal film formed on the insulating film. Respective convex portions constituting the multiple concavities and convexities are formed into shapes in which positions of peak portions relative to the entire convex portions are tilted in one direction when viewed from a direction of a normal line of the substrate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a reflector, a liquid crystal display(LCD) device having the reflector, a method of manufacturing areflector, and a method of manufacturing an LCD device having thereflector. More specifically, the present invention relates to astructure of a reflector to be formed on a substrate of an LCD device, areflective or semi-transmissive LCD device having the reflector, andmethods of manufacturing the reflector and the LCD device having thereflector.

2. Description of the Related Art

LCD devices have favorable features of small sizes, thin profiles, andlower power consumption and are therefore put into practical use in abroad range of applications including office automation equipment, andportable devices. Unlike a cathode ray tube (CRT) or anelectroluminescence (EL) display device, LCD devices do not include alight-emitting function by themselves. Accordingly, a transmissive LCDdevice is provided with a backlight source so that displays arecontrolled by transmission amount of backlight through an LCD panel. Byuse of the backlight, this transmissive LCD device can achieve a brightscreen without depending on ambient environments. On the other hand,this type of the LCD device has a problem of short operating time inmobile use particularly when it is driven by a battery power source.This is because the backlight source consumes high power during displayoperation.

A reflective LCD device configured to display images by use of ambientlight has been proposed in order to solve the problem of high powerconsumption by the backlight source. This reflective LCD device isprovided with a reflector instead of the backlight source, so thatdisplays are controlled by transmission amount of the ambient lightreflected by the reflector through the LCD panel. Thus, by employingsuch a reflective LCD device, it is possible to aim to achieve reductionin power consumption as well as reduction in size and weight. In themeantime, this LCD device has a problem of deterioration in visibilityin a dark ambient environment.

Accordingly, there is disclosed an LCD device in which each pixelincludes a transmissive region and a reflective region in order toprevent an increase in power consumption attributable to the backlightsource and deterioration in visibility attributable to the ambientenvironment. An LCD device having both functions of the transmissive LCDdevice and the reflective LCD device will be hereinafter referred to asa semi-transmissive reflective LCD device. Usually, thissemi-transmissive reflective LCD device is configured to form areflector at a part (a reflective region) of an active-matrix substrateincluding switching elements such as thin film transistors (TFTs) and togenerate diffuse reflection of ambient light by use of this reflector.

The reflective LCD device or the semi-transmissive reflective LCD deviceis provided with a resin layer having a concavo-convex shape and thenthe reflector is formed by providing a reflective film on the resinlayer. This LCD device pursues a bright display under a condition ofstrong external light by applying this structure. The concavo-convexshape of the resin layer is formed by exposing and developing portionsto be concavities and convexities by a photolithography method and thensubjecting these portions to a heat treatment. However, by using themanufacturing methods and the structures of the related art, it isdifficult to fabricate a reflector having a sufficiently brightreflection characteristic at low costs.

SUMMARY OF THE INVENTION

Accordingly, an exemplary feature of the present invention is to providea structure of a reflector having a bright reflection characteristicobtained by effectively reflecting incident light toward a viewer, andto provide a method of manufacturing the reflector.

Another exemplary feature of the present invention is to provide an LCDdevice including the reflector and a method of manufacturing the LCDdevice.

A reflector according to the present invention is configured to reflectincident light from outside and includes an insulating film being formedon a substrate and having multiple concavities and convexities, and ametal film formed on the insulating film. Here, convex portionsconstituting the multiple concavities and convexities are formed intoshapes in which the positions of peak portions respectively in theentire convex portions are tilted in one direction when viewed from adirection of a normal line of the substrate.

Another reflector according to the present invention is configured toreflect incident light from outside and includes an insulating filmbeing formed on a substrate and having multiple concavities andconvexities, and a metal film formed on the insulating film. Here, atilted portion is a portion between a peak portion of each of the convexportions constituting the multiple concavities and convexities and aconcave portion around the convex portion. As for the tilt angle of thetilted portion to the surface of the substrate, the tilt angle on acertain side is smaller than the tilt angle on another side.

Still another reflector according to the present invention is configuredto reflect incident light from outside and includes an insulating filmbeing formed on a substrate and having multiple concavities andconvexities, and a metal film formed on the insulating film. Here, atilted portion between each of the convex portions constituting themultiple concavities and convexities and a concave portion around theconvex portion has a slope which is relatively longer on a predeterminedside than a slope on another side.

Preferably, the concavities and the convexities are formed by arranginga pattern which applies at least a partial side of any of a polygon, acircle and an ellipse to any of the convex portion and the concaveportion, or formed by arranging a pattern which applies any of a wavyline or a winding line to any of the convex portion and the concaveportion.

Preferably, the insulating film is a resin film.

A liquid crystal display device according to the present inventionincludes a pair of substrates and a liquid crystal layer interposedbetween the pair of substrates, wherein a reflector having above featureis formed on either one of the pair of substrates.

A method of manufacturing a reflector according to the present inventionfor reflecting incident light from outside includes the steps of coatingphotosensitive resin on a substrate, exposing the photosensitive resinby use of a photomask having a light-shielding region where a pattern isformed in a size equal to or larger than a resolution limit, a firsttransmissive region where a pattern is formed in a size smaller than theresolution limit, and a second transmissive region having higher opticaltransmittance than the first transmissive region, performing developmentof the photosensitive resin after the exposure and forming three regionshaving different film thicknesses, subjecting the photosensitive resinto a heat treatment after the development, and forming a reflective filmon the photosensitive resin after the heat treatment.

Preferably, the photomask includes a pattern in which any of polygons,circles, and ellipses are arranged in a plane direction while a side ofany of each polygon, circle, and ellipse constitutes the light-shieldingregion, and the first transmissive region is located adjacent to thelight-shielding region.

Preferably, the photomask includes a pattern in which any of wavy linesand winding lines are arranged in a plane direction while any of eachwavy line and winding line constitutes the light-shielding region, andthe first transmissive region is located adjacent to the light-shieldingregion.

Preferably, the photomask includes a pattern in which any of polygons,circles, and ellipses in a plane direction while a side of any of eachpolygon, circle, and ellipse constitutes the second transmissive region,and the first transmissive region and the light-shielding region arelocated adjacent to each other in areas surrounded by sides of any ofthe polygons, circles, and ellipses.

Preferably, the photomask includes a pattern in which any of wavy linesand winding lines are arranged in a plane direction while any of eachwavy line and winding line constitutes the second transmissive region,and the first transmissive region and the light-shielding region arelocated adjacent to each other at portions other than any of the wavylines and winding lines.

Preferably, the pattern in the size smaller than the resolution limit ischanged stepwise in the first transmissive region.

Preferably, a light-shielding pattern is not formed in the secondtransmissive region.

As described above, according to the present invention, the reflector isformed such that the respective convex portions constituting theconcavities and convexities have the peak portions that are tilted inthe same direction. Thus, it is possible to increase a reflectivecomponent in a required direction. In this way, it is possible to obtaina reflector having a bright reflection characteristic and a high visualquality LCD device including the reflector. As to the shapes of the peakportions tilted in the same direction, it is conceivable to employ anyone of a configuration in which the tilt angle is relatively smaller onthe light incident side and a configuration in which the length of theslope is relatively longer on the light incident side.

In the case of a diffuse reflector fabricated in accordance with aphotolithography method of the related art, the light incident fromoutside is reflected isotropically by a cross section of the concavitiesand convexities while centering on a specular direction as shown in FIG.7A. For this reason, the light scatters not only in the speculardirection but also in the opposite direction relative to a viewer. Onthe contrary, in the case of the diffuse reflector according to thepresent invention, the tilt angle of the tilted portions on the lightincident side is formed small, or alternatively, the length of theslopes on the light incident side is formed long. Accordingly, it ispossible to condense the light efficiently along the direction of thenormal line of the substrate (the direction toward the viewer) as shownin FIG. 7B. Moreover, it is possible to make efficient use of theincident light from various directions by arranging basic figures suchas polygons or circles to form the concavities and convexities.

Further, according to the present invention, the photomask used for aphotolithographic process is formed into a combination of thelight-shielding region having the pattern in the size equal to or largerthan the resolution limit, the first transmissive region having thepattern in the size smaller than the resolution limit, and the secondtransmissive region having the higher optical transmittance than thefirst transmissive region. In this way, it is possible to form threeregions having different exposure amounts at the same time. Thisphotomask can be fabricated in accordance with existing processes.Moreover, the process for fabricating the reflector is also simplified.Accordingly, the tact time is reduced and the production yield isimproved. Due to these advantages, it is possible to fabricate thereflector having a bright reflection characteristic and the LCD deviceincluding the reflector at low costs.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and advantages and further description of theinvention will be more apparent to those skilled in the art by referenceto the description, taken in connection with the accompanying drawings,in which:

FIGS. 1A to 1E are cross-sectional process drawings schematicallyshowing a method of manufacturing a reflector according to a firstexemplary embodiment of the present invention;

FIGS. 2A to 2H are plan views showing patterns of photomask used formanufacturing the reflector according to the first exemplary embodimentof the present invention;

FIGS. 3A and 3B are plan views showing comparison of patterns between aphotomask of the related art and a photomask used in the first exemplaryembodiment;

FIG. 4A is a photograph showing external appearance of a reflectorfabricated by use of the photomask of the related art and FIG. 4B is aphotograph showing external appearance of the reflector fabricated byuse of the photomask of the first exemplary embodiment;

FIG. 5 is a diagram for explaining a method of measuring reflectance;

FIG. 6 is a graph showing reflection characteristics of the reflector ofthe related art and the reflector of the first exemplary embodiment;

FIG. 7A is a diagram schematically showing the reflection characteristicof the reflector of the related art and FIG. 7B is a diagramschematically showing the reflection characteristic of the reflector ofthe first exemplary embodiment;

FIG. 8 is a plan view showing a structure of a semi-transmissivereflective LCD device according to a second exemplary embodiment of thepresent invention;

FIG. 9 is a cross-sectional view of the semi-transmissive reflective LCDdevice which is taken along the I-I line in FIG. 8;

FIGS. 10A to 10C, 11A and 11B are cross-sectional views to explain amethod of manufacturing the semi-transmissive reflective LCD deviceaccording to the second exemplary embodiment of the present invention;

FIG. 12 is a cross-sectional view showing another structure of thesemi-transmissive reflective LCD device according to the secondexemplary embodiment of the present invention;

FIG. 13 is a view for explaining specular reflection of incident light;

FIGS. 14A and 14B are schematic diagrams for explaining actual workingconditions of an LCD device; and

FIGS. 15A to 15E are cross-sectional process drawings for explaining amethod of manufacturing a reflector of the related art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Prior to explaining the preferred embodiments of the present invention,a reflector according to the related art and an LCD device using thisreflector will be described below.

An LCD device including a reflector often employs a diffuse reflectorconfigured to diffuse incident light. It is because glare is apt tooccur in a specular direction relative to a substrate by influences ofvarious layers constituting the LCD device in a case where light isincident from a light source, and such glare may degrade displayquality. As shown in FIG. 13, the various layers may include a polarizer19 b, a retarder 20 b, a transparent insulating substrate 13, a counterelectrode 15, a liquid crystal layer 17, and the like. Meanwhile,visibility is deteriorated by use of a mirror reflector due to darknessin directions other than the specular direction. The use of the diffusereflector is therefore preferred.

As a method for manufacturing a diffuse reflector of this kind, forexample, Japanese Patent No. 3,394,926 discloses a method including astep of subjecting photosensitive resin to exposure by use of aphotomask in which a total area of circles or polygons occupies 20% to40% (inclusive) of a total area of the photomask. As shown in FIGS. 15Ato 15E, this manufacturing method is configured to perform exposure onthe photosensitive resin by use of the photomask having a circular orpolygonal pattern in order to form two types of regions, namely, exposedregions and shielded regions. In a case where positive photosensitiveresin is used, for example, the exposed regions are formed into concaveportions while the shielded portions are formed into convex portionsafter development. Then, required slopes are formed on a surface bysubjecting the photosensitive resin to a heat treatment. In a case wherea photomask having a circular pattern is used, for example, it ispossible to obtain only symmetric cross sections. As shown in FIG. 7A,external light incident on the reflector scatters isotropically whilecentering on a specular direction. Here, actual working conditions of anLCD device will be considered. As shown in FIG. 14A, when the LCD deviceis used for a cellular telephone 41, for example, an LCD panel 41 a isused at a tilted angle relative to a horizontal direction. A directionof a viewer is shifted from the specular direction toward a verticaldirection of the panel relative to the incident light. That is, this LCDdevice utilizes reflected light in the direction shifted from thespecular direction toward the vertical direction of the panel.Meanwhile, as shown in FIG. 14B, an LCD panel 42 a embedded in a devicesuch as a personal digital assistant (PDA) 42 designed to be operatedwith a stylus is frequently used in an almost horizontal state.Therefore, this liquid crystal device is used at an angle closer to aspecular component as compared to the cellular telephone 41. Here,reflected light in the specular direction is mainly used as compared tolight close to the vertical direction of the panel. Nevertheless, verylittle light components in the reverse direction to the verticaldirection of the panel,relative to the specular direction are used for adisplay purpose. Accordingly, the reflector designed for isotropic lightscattering causes light losses. Thus, the reflector having a brightreflection characteristic cannot be manufactured.

In the meantime, to improve a reflection characteristic in an arbitrarydirection, Japanese Patent Laid-Open Publication No. 2002-207214discloses a structure of a reflector in which a surface has aconcavo-convex shape, and lines connecting convex portions out of theconcavo-convex shape, lines connecting concave portions out of theconcavo-convex shape, and lines connecting intermediate portions betweenthe convex portions and concave portions include many componentssubstantially orthogonal to a direction connecting the viewer to thelight source. In this way, improvement of the reflection characteristicin an arbitrary direction is pursued. However, this method also employsa photomask similar to Japanese Patent No. 3,394,926. Thus, across-sectional shape of a component substantially orthogonal to thedirection connecting the viewer to the light source is isotropic asshown in FIG. 7A. For this reason, this reflector also causes lightlosses as in the case of Japanese Patent No. 3,394,926. Thus, thereflector having a bright reflection characteristic cannot bemanufactured.

To solve this problem, Japanese Patent Laid-Open Publication No.2004-037946 discloses a structure of a reflector including a firsttilted resin layer disposed on a substrate and a second tilted resinlayer disposed on the first tilted resin layer. In this manufacturingmethod, the tilted resin layers are respectively fabricated inaccordance with a mode of employing a method using a halftone maskaccording to a shifter method, a mode of controlling a film loss by useof light interference while using a mask having two types of rectanglesindifferent sizes, and a mode of performing exposure while moving aphotomask in parallel. Nevertheless, it is complicated to design andfabricate the halftone masks according to the shifter method. Meanwhile,the mask having the two types of rectangles in the different sizes usesthe light interference. Thus, precision of a mask pattern has a largeimpact on exposure accuracy. Hence it is difficult to obtain a uniformconcavo-convex pattern. The mode of performing exposure while moving thephotomask in parallel requires two exposure sessions while moving thephotomask. Here, the concavo-convex shape is apt to vary because it isdifficult to align an exposure position in the first session with anexposure position in the second session. In addition, it is necessary torepeat the photolithographic processes twice for forming the firsttilted resin layer and the second tilted resin layer severally. For thisreason, occurrence of variation in the shape attributed to misalignmentof the photomasks and an increase in the number of processes lead toreduction in yields. Accordingly, it is difficult fabricate a reflectorhaving a bright reflection characteristic at low costs.

A reflector according to a preferred embodiment of the present inventionprovides a diffuse reflector configured to diffuse and reflect incidentlight toward an arbitrary direction, which includes concavities andconvexities in a shape such that peak portions are displaced in the samedirection. Preferably, the shape such that the peak portions aredisplaced in the same direction is achieved by forming tilted portionsbetween the peak portions of respective convex portions and concaveportions around the convex portions such that a tilt angle is definedrelatively smaller on a light incident side or that a length of a slopis relatively longer on the light incident side. In this way, a brightreflection characteristic is obtained by increasing components along aview direction by a viewer in an actual working condition. Moreover,this diffuse reflector is fabricated by use of a photomask whichincludes a combination of a light-shielding region having a pattern in asize equal to or larger than a resolution limit, a first transmissiveregion having a dot or stripe pattern in a size smaller than theresolution limit, and a second transmissive region having higher opticaltransmittance than the first transmissive region.

This photomask allows formation of anisotropic shapes of the concavitiesand convexities by one session of exposure, which has not been availableby a conventionally used photolithography method configured to partiallyapply a pattern in a size equal to or larger than the resolution limit.In this way, it is possible to increase reflective components in arequired direction while decreasing reflective components in unwanteddirections. In addition, by forming the concavities and convexities byarranging basic figures such as polygons or circles, it is possible toreflect light that is incident from various directions efficientlytoward the viewer. In this way, it is possible to obtain a reflectorhaving a sufficiently bright reflection characteristic and a high visualquality LCD device including the reflector by simple manufacturingprocesses, at high yields and at low costs.

First Exemplary Embodiment

A reflector and a manufacturing method thereof according to a firstexemplary embodiment of the present invention will be described withreference to the accompanying drawings. As shown in FIG. 1E, thereflector of this embodiment includes an insulating film 11 formed on asubstrate 8 and provided with multiple concavities and convexities, anda metal film 6 formed on the insulating film 11. In particular,respective convex portions constituting the multiple concavities andconvexities are formed into shapes in which positions of peak portionsrelative to the entire convex portions are tilted in the same directionwhen viewed from a direction of a normal line of the substrate 8.

Now, a method of manufacturing the reflector of this embodiment will beconcretely described with reference to FIGS. 1A to 1E. First, as shownin FIG. 1A, positive photosensitive resin 11 a is coated in a filmthickness ranging from about 0.5 μm to 5 μm on the given substrate 8. Inthis embodiment, the film thickness is set approximately equal to 2.2μm, for example. A transparent insulating substrate such as glass orplastics for fabricating an active-matrix substrate of an LCD device ina second exemplary embodiment to be described later is used herein asthe given substrate 8, for example. As the positive photosensitive resin11 a, PC403 (product name) manufactured by JSR Corporation is used, forexample.

Next, as shown in FIG. 1B, a photomask 32 is placed above thephotosensitive resin 11 a. Then, the photosensitive resin 11 a issubjected to exposure by use of the photomask.32. This photomask 32includes three regions which are a light-shielding region 31 a providedwith a light-shielding film 30 a having a pattern in a size equal to orlarger than a resolution limit, a first transmissive region 31 b locatedadjacent to the fight-shielding region 31 a and provided with alight-shielding film 30 b having a pattern in a size smaller than theresolution limit, and a second transmissive region 31 c where no patternis formed. The first transmissive region 31 b has higher opticaltransmittance than the light-shielding region 31 a. Meanwhile, since nopattern is formed in the second transmissive region 31 c, the secondtransmissive region 31 c has higher optical transmittance than the firsttransmissive region 31 b.

Widths, locations, and shapes of the light-shielding region 31 a, thefirst transmissive region 31 b, and the second transmissive region 31 ccan be set up as appropriate. Here, as shown in FIG. 2E and FIG. 3B, amask in which hexagons each having a side thickness equal to about 2.5μm and an average side length equal to about 18 μm are irregularlyarranged in a plane direction with addition of line patterns having athickness of about 1 μm located inside the sides in a given direction ofthe hexagons is used. Exposure is conducted through this mask by use ofthe g line (436 nm) and the h line (405 nm) from a high-pressure mercurylamp as a light source. In this case, the resolution limit is equal toabout 2 μm. Since the light-shielding region 31 a corresponding to thesides of the hexagons has the thickness of about 2.5 μm, thelight-shielding region 31 a has the larger size than the resolutionlimit and is therefore sufficiently imaged. The first transmissiveregion 31 b where the line patterns having the thickness of about 1 μmfalls below the resolution limit and is therefore not imagedsufficiently. Moreover, the light is partially shielded by the linepatterns in the first transmissive region 31 b. Therefore, an integratedvalue of light exposure in the first transmissive region 31 b is smallerthan an integrated value of light exposure in the second transmissiveregion 31 c without patterns. In the meantime, the integrated value oflight exposure in the first transmissive region 31 b is higher than anintegrated value of light exposure in the light-shielding region 31 a.Here, the integrated value of the light exposure in the secondtransmissive region 31 c is set to an appropriate amount so as topreserve approximately 50% of the photosensitive resin afterdevelopment. When this photomask is used for performing exposure anddevelopment, it is possible to form a concavo-convex film 11 byarranging concave portions in random hexagonal shapes. Thisconcavo-convex film 11 includes convex portions defined by ridgesbetween the concave portions.

Here, the concavo-convex pattern is described as the shape defined byirregularly arranging the hexagons. However, the shape of the pattern isnot particularly limited. For example, as shown in FIGS. 2A to 2C, it isalso possible to arrange other polygons such as triangles, pentagons orhexagons regularly. When any of these photomasks is used for performingexposure and development, it is possible to form the concavo-convex film11 by arranging concave portions in polygonal shapes such as triangles,pentagons or hexagons. This concavo-convex film 11 includes ridgesbetween the concave portions. As shown in FIG. 2D, it is possible toform the inside of the polygons into light-shielding patterns. When thephotomask shown in FIG. 2D is used for performing exposure anddevelopment, it is possible to form the concavo-convex film 11 byarranging triangular convex portions. Meanwhile, it is possible to forma circular or ellipsoidal pattern as shown in FIG. 2F. When thephotomask shown in FIG. 2F is used for performing exposure anddevelopment, it is possible to form the concavo-convex film 11 byarranging circular convex portions. Moreover, it is also possible tomodify the pattern into wavy lines as shown in FIG. 2G or winding linesas shown in FIG. 2H.

Although the line patterns having the thickness of about 1 μm are formedin the first transmissive region 31 b in the foregoing case, it issatisfactory as long as the thickness is set equal to or below 2 μm inthe case of using the above-described light source. Alternatively, it isalso possible to form finer patterns by use of a light source having ashorter wavelength and a reduction exposure system. In this case, the iline of a high-pressure mercury lamp or an excimer laser is applicableto the light source having the shorter wavelength, for example.

Next, as shown in FIG. 1C, a development process is conducted by use ofa developer such as tetramethyl ammonium hydroxide (TMAH), for example,thereby removing exposed portions. In this embodiment, the filmthicknesses of the photosensitive resin 11 a is adjusted to about 2.2 μmequivalent to the original film thickness for the light-shielding region31 a, about 1.5 μm for the first transmissive region 31 b, and about 1.1μm for the second transmissive region 31 c after the developmentprocess.

Next, the photosensitive resin 11 a formed into the concavities andconvexities is subjected to baking at about 220° C. for about 2 hours.In this way, the concavo-convex film 11 is formed into a smoothconcavo-convex shape as shown in FIG. 1D. Then, as shown in FIG. 1E,metal such as an Al—Nd alloy is deposited on the concavo-convex film 11by sputtering or the like to form a reflective film 6.

Although the above-described manufacturing method employs the positivephotosensitive resin as the photosensitive resin, it is also possible toemploy negative photosensitive resin hereto. In this case as well, it ispossible to form three regions having different light exposure amountsat the same time. As for the film thicknesses of the photosensitiveresin after development, the first transmissive region 31 b bears thethicker resin than that on the second transmissive region 31 c, and thelight-shielding region 31 a bears the thicker resin than that on thefirst transmissive region 31 b.

Moreover, in this embodiment, the light-shielding pattern in the firsttransmissive region 31 b is formed along a certain side out of the sidesof each polygon. Instead, it is possible to form a dot pattern or tocombine the line pattern with the dot pattern. It is also possible tochange density of the line pattern or the dot pattern stepwise so as tochange the optical transmittance stepwise. Furthermore, the opticaltransmittance of the first transmissive region 31 b can be setappropriately in response to the tilt angle. In a case where the opticaltransmittance of the second transmissive region 31 c is assumed to beequal to 100%, the optical transmittance of the first transmissiveregion 31 b is preferably set in a range from about 20% to about 80%inclusive.

Next, effects of the reflector fabricated in accordance with theabove-described method will be described. As shown in FIG. 4A, areflector fabricated by use of a photomask of the related art shown inFIG. 3A has features of approximately equal tilt angles between tiltedportions from peak portions of respective convex portions towardsurrounding concave portions and of almost constant lengths of slopes.Dark portions in FIG. 4A represent the tilted portions from the peakportions of the respective convex portions toward the surroundingconcave portions.

As shown in FIG. 4B, it is apparent that the reflector fabricated by useof the photomask of this embodiment shown in FIG. 3B has a smaller tiltangle at the tilted portion corresponding to the region having thepattern in the size smaller than the resolution limit, and a longerslope, corresponding to the tilted portion. Apparently, the length ofthe slope at the tilted portion, namely, a distance from the peakportion of the convex portion to the concave portion is increased. Darkportions in FIG. 4B represent the tilted portions from the peak portionsof the respective convex portions toward the surrounding concaveportions.

Now, a method of measuring reflectance of the reflector will bedescribed with reference to FIG. 5. A direction of a normal line of anLCD panel 40 including the reflector is defined as a reference, andreflection of light which is incident by use of a projector from adirection of −30° is captured with photodetectors located in a directionof 0° and in a direction of 10°. The reflectance is measured in thisway. As shown in FIG. 6, when the light incident from the direction of−30° is diffused and reflected by a standard while plate, thereflectance of the reflected light captured in the direction of 0° isdefined as 100%. The light incident from the direction of −30° isdiffused and reflected by the reflector to be measured, and thereflected light is captured in the direction of 0°. FIG. 6 showsrelative reflectance to the reflectance by the standard white plate.Here, WS-3 (product name) manufactured by Topcon Corporation is used asthe standard white plate. This standard white plate is made of BaSO₄,for example.

In FIG. 6, a dotted solid line shows the reflectance of the reflectorfabricated by use of the photomask of this embodiment. A solid linewithout dots shows the reflectance of the reflector fabricated by use ofthe photomask of the related art shown in FIG. 3A. It is apparent fromFIG. 6 that the reflector fabricated by use of the photomask of thisembodiment including the patterns in the smaller size than theresolution limit can improve the reflectance as compared to thereflector of the related art. As shown in FIG. 7A, the symmetricconcavo-convex pattern of the related art reflects the incident lightisotropically and thereby generates more components in unwanteddirections. On the contrary, in the concavo-convex patter of thisembodiment, the tilted portions each having a smaller tilt angle or alonger slope are located on the light incident side. In this way, it ispossible to increase components to be reflected to a viewer whiledecreasing components in unwanted directions. In addition, as a resultof sensory evaluation with eyes under the situation illustrated in FIG.14A, it is confirmed that the display is obviously brighter and thatdeterioration of visibility is not observed when moving the position ofthe light source.

According to this embodiment, it is possible to form the concavities andconvexities provided with the tilted portions having the smaller tiltangles or longer slopes by use of the photomask 32 that includes thelight-shielding region 31 a provided with the pattern in the size equalto or larger than the resolution limit, the first transmissive region 31b located adjacent to the light-shielding region 31 a and provided withthe pattern in the smaller size than the resolution limit, and thesecond transmissive region 31 c without patterns which is locatedoutside the first transmissive region 31 b. It is possible to increase areflective component in the direction of the normal line of thesubstrate by locating the tilted portions having smaller tilt angles orlonger slopes on the light incident side. In other words, it is possibleto increase the reflective components along a view direction by a viewerin an actual working condition. Therefore, it is possible to fabricatethe reflector having a bright reflection characteristic at low costswhile decreasing the components in unwanted directions.

Second Exemplary Embodiment

Next, an LCD device and a manufacturing method thereof according to asecond exemplary embodiment of the present invention will be describedwith reference to the accompanying drawings. FIG. 9 shows asemi-transmissive reflective LCD device in which a twist angle is setapproximately equal to 72° and a cell gap in a reflective region isequal to a cell gap in a transmissive region. FIG. 12 shows asemi-transmissive reflective LCD device in which a twist angle is setapproximately equal to 0° and a cell cap in a reflective region isdifferent from a cell gap in a transmissive region.

As shown in FIG. 8 and. FIG. 9, the semi-transmissive reflective LCDdevice of this embodiment includes an active-matrix substrate 12 onwhich thin film transistors (TFTs) 3 serving as switching elements areformed, a counter substrate 16, a liquid crystal layer 17 sandwichedbetween the two substrates 12 and 16, a backlight source 18 disposed ona back side of the active-matrix substrate 12, retarders 20 a and 20 bas well as polarizers 19 a and 19 b provided outside the active-matrixsubstrate 12 and outside the counter substrate 16, respectively. As tothe retarders 20 a and 20 b, λ/4 plates are employed.

Moreover, the active-matrix substrate 12 includes a transparentinsulating substrate 8, a gate line (a scan electrode) 1, a commonstorage line 4, an auxiliary capacitance electrode 4 a, a gate electrode1 a, a gate insulating film 9, a semiconductor layer 3 a, a drainelectrode 2 a, a source electrode 2 b, a data line (a signal electrode)2, a passivation film 10, and a pixel electrode. The gate electrode 1 a,the gate insulating film 9, the semiconductor layer 3 a, the drainelectrode 2 a, and the source electrode 2 b collectively constitutes theTFT 3.

The gate line 1, the gate electrode la connected to the gate line 1, thecommon storage line 4, and the auxiliary capacitance electrode 4 a areformed on the transparent insulating substrate 8. The gate insulatingfilm 9 is formed on these constituents. The semiconductor layer 3 a isformed on the gate insulating film 9. The drain electrode 2 a and thesource electrode 2 b are drawn out of two ends of the semiconductorlayer 3 a and are formed on the gate insulating film 9. The drainelectrode 2 a is connected to the data line 2. The passivation film 10is formed so as to cover the data line 2, the drain electrode 2 a, thesource electrode 2 b, and the semiconductor layer 3 a. A pixel electrode(a transparent electrode film 5) is connected to the source electrode 2b. The pixel electrode is provided one by one on an intersection of thesignal electrode 2 and the scan electrode 1. Moreover, a pixel region PXincludes a transmissive region PXa for transmitting incident light fromthe backlight source 18 and a reflective region PXb for reflectingexternal ambient light which is incident thereon. A concavo-convex film11 made of an organic film or the like is formed on the passivation filmin the pixel region PX. A reflective film 6 containing aluminum (Al) oran aluminum (Al) alloy, is formed in the reflective region PXb. Thisreflective film 6 is interposed between the concavo-convex film 11 and asecond passivation film 24 and is thereby isolated from othersurrounding constituents. Here, since it is not necessary to use themetal film formed in the reflective region PXb as an electrode, thismetal film is referred to as the reflective film 6. This reflective film6 is located above the TFT 3, so that the TFT 3 is covered with thereflective film 6. The transparent electrode film 5 made of indium tinoxide (ITO) or the like is formed on the entire surface of each pixelregion PX while interposing the second passivation film 24 so as tocover the reflective film 6. The transparent electrode film 5 isconnected to the source electrode 2 b of the TFT 3 through a contacthole 7 provided on the concavo-convex film 11. The transparent electrodefilm 5 functions as the pixel electrode. An alignment film 29 made ofpolyimide or the like is formed on this transparent electrode film 5.

Meanwhile, the counter substrate 16 includes a transparent insulatingsubstrate 13, a color filter 14, a black matrix (not shown), a counterelectrode 15, an alignment film 29, and the like. The twist angle ofthis semi-transmissive reflective LCD device is set approximately equalto 720. In this way, a cell gap dr of the reflective region PXb is setequal to a cell gap df of the transmissive region PXa. Here, the cellgaps dr and df are set equal to 2.7 μn.

By covering the TFT 3 with the reflective film 6 as describedpreviously, it is possible to block the external ambient light with thereflective film 6 when this light is incident on the TFT 3. In this way,it is possible to prevent occurrence of a malfunction attributable to anincrease in an off-state current on the TFT 3 owing to a photoelectriceffect caused by the incident light. However, if there is a shortdistance between the reflective film 6 and the TFT 3, a voltage (a gatevoltage, in particular) to be applied to the TFT 3 may induce variationin electric potential of the reflective film 6 in an electricallyfloating state and may thereby disturb an electric field for liquidcrystal control. Therefore, in this embodiment, the concavo-convex film11 is also formed on the TFT 3 so as to secure the distance between theTFT 3 and the reflective film 6 by interposition of the concavo-convexfilm 11, thereby relieving an adverse effect on the reflective film 6attributable to the voltage applied to the TFT 3.

Next, a method of manufacturing the semi-transmissive reflective LCDdevice having the above-described configuration will be described in theorder of manufacturing steps with reference to FIG. 10A to FIG. 11B.Here, a method of manufacturing a gate-drain (G-D) conversion portionand a possible to form the three regions having different filmthicknesses after development, the concavo-convex film 11 can befabricated in fewer processes and at a high yield.

Although this embodiment uses the TFTs made of amorphous silicon as theswitching elements, it is also possible to use TFTs made ofpolycrystalline silicon or other elements (such as thin film diodes(TFDs)). Moreover, the present invention can also achieve a finecharacteristic when applied to a reflector for a passive-matrix LCDdevice without any switching elements.

Meanwhile, the semi-transmissive reflective LCD device of FIG. 9 employsthe liquid crystal having the twist angle approximately equal to 72°.Moreover, the cell gap dr in the reflective region PXb is set equal tothe cell gap df in the transmissive region PXa. That is, theconcavo-convex film 11 is formed substantially in the same thickness inboth of the reflective region PXb and the transmissive region PXa. In acase where the twist angle of the liquid crystal is set in a range fromabout 0° to 60°, it is possible to obtain optimum intensity of theoutgoing light by setting the cell gap dr and the cell gap df tomutually different values.

FIG. 12 is a cross-sectional view showing a semi-transmissive reflectiveLCD device according to a first modified example of this embodiment. Asshown in FIG. 12, in this semi-transmissive reflective LCD device, thetwist angle of the liquid crystal is set approximately equal to 0° andthe concavo-convex film 11 is formed only in the reflective region PXb.The cell gap df in the transmissive region PXa is set equal terminalportion to be located in a peripheral region of the active-matrixsubstrate 12 will also be described at the same time. The G-D conversionportion is configured to prevent a short circuit between outgoing linescaused by electrically conductive sealing. In a case where it isnecessary to draw the drain electrode 2 a electrically to outside, it ishardly possible to draw the drain electrode 2 a directly to the outsidewithout causing a short circuit due to structural restrictions.Therefore, this G-D conversion portion is provided in order to draw outthe drain electrode 2 a by use of the gate line 1 through thetransparent electrode film 5.

First, as shown in FIG. 1A, metal such as Chromium (Cr) is deposited onthe entire surface of the transparent insulating substrate 8 made ofglass, plastics, or the like, and then the gate line 1, the gateelectrode 1 a, the common storage line 4, and the auxiliary capacitanceelectrode 4 a are formed by removing the unnecessary metal by use ofpublicly-known photolithographic techniques and etching techniques. Notethat the constituents not shown in FIG. 9 are illustrated in FIG. 8.Next, the gate insulating film 9 made of SiO₂, SiNx, SiOx or the like isformed on the entire surface. Then, the semiconductor layer 3 a isformed by depositing and then patterning amorphous silicon (a-Si) or thelike on the entire surface. Subsequently, after depositing metal such asCr on the entire surface, the data line 2, the drain electrode 2 a, thesource electrode 2 b, and a storage electrode 2 c for capacitance, areformed by patterning. In this way, the TFT 3 is formed. Thereafter, thepassivation 10 made of a SiNx film or the like for protecting the TFT 3is deposited on the entire surface in accordance with a plasma-enhancedchemical vapor deposition (plasma CVD) method or the like. Meanwhile,the G-D conversion portion and the terminal portion are placed outsidethe pixel region PX on the transparent insulating substrate 8.

Next, as shown in FIG. 10B, photosensitive acrylic resin such as PC403,415G or 405G manufactured by JSR Corporation is coated on thepassivation film 10 by a spin coating method, for example, and theconcavo-convex film 11 is formed in the pixel region PX by subjectingthe photosensitive resin to exposure and development.

This concavo-convex film 11 is formed by performing exposure anddevelopment while using the photomask as shown in FIG. 1B, for example.To be more precise, the photomask used herein includes thelight-shielding region 31 a fabricated with a pattern in a size equal toor larger than the resolution limit so as to correspond to convexportions of the concavo-convex film 11, the first transmissive region 31b formed with a pattern in a size smaller than the resolution limit, thesecond transmissive region 31 c designed to achieve higher opticaltransmittance than the first transmissive region 31 b so as tocorrespond to concave portions, and a third transmissive region formedin positions corresponding to the contact hole 7, the G-D conversionportion, and the terminal portion where no pattern is provided. Thisthird transmissive region has higher optical transmittance than thesecond transmissive region. For example, no light-shielding pattern isformed herein. The, photosensitive acrylic resin is subjected toexposure by use of the photomask having the above-described features.

Here, it is also possible to remove the photosensitive resin completelyin the region for forming the contact hole 7 and the regions for formingthe G-D conversion portion and the terminal portion by performingexposure at relatively higher optical intensity while using a differentphotomask.

Thereafter, the concavities and convexities are formed by use of analkaline developer while utilizing differences in rates of dissolutionwith an alkaline solution among the concave portions, the convexportions, the contact hole 7, and the like. After development, thephotosensitive acrylic resin is completely removed in the positionscorresponding to the contact hole 7, the G-D conversion portion, and theterminal portion. Meanwhile, the concavo-convex film 11 is formed in thepixel region PX. Accordingly, it is possible to form the concave-convexshape of the concavo-convex film 11 in one session of exposure by use ofthe photomask having the above-described features. Specifically, theconcavo-convex film 11 is formed such that the tilt angle is decreasedin the tilted portion corresponding to the pattern having the smallersize than the resolution limit while the length of the slope at thatportion is increased as shown in FIG. 4B. In other words, theconcavo-convex film 11 is formed such that the distance between the peakportion of the convex portion and the concave portion is increased. Thecontact hole 7 is formed simultaneously with formation of theconcavo-convex shape of the concavo-convex film 11, and the regionsconstituting the G-D conversion portion and the terminal portion areexposed. It is to be noted that although the concavo-convex film 11 isformed all over the pixel region PX including the reflective region PXband the transmissive region PXa in the drawing, it is also possible toplanarize the surface of the concavo-convex film 11 formed in thetransmissive region Pxa without providing the concavities and theconvexities. Moreover, in a case where the concavo-convex film 11 isformed in the transmissive region PXa, the acrylic film is decolorizedby performing the exposure process on the entire surface so as tosuppress attenuation of the incident light by the concavo-convex film11. Thereafter, the acrylic film is cured at 220° C. for about one hourto finish the concavo-convex film 11 having the smaller tilt angle atthe tilted portion or the longer slope.

As described previously, if a gap between the TFT 3 and reflective film6 is too narrow, there is a risk of incurring variation in the electricpotential of the reflective film 6 attributable to the gate voltage orthe like to be applied to the TFT 3, and deterioration in the displayquality as a consequence of the variation that disturbs the electricfield for liquid crystal control. Therefore, the concavo-convex film 11is also formed on the TFT 3 in this embodiment.

Next, the reflective film 6 is formed in the reflective region PXb outof the pixel region PX as shown in FIG. 10C. For example, metal such asaluminum (Al) or an aluminum (Al) alloy is deposited on the entiresurface in accordance with a sputtering method or a vapor depositionmethod. Thereafter, only the reflective region PXb out of the pixelregion PX is covered with a resist pattern. The reflective film 6 isformed by partially dry-etching or wet-etching the exposed metal whileusing this resist pattern as a mask. Here, the reflective film 6 isformed on the TFT 3 as well so that the external ambient light is notincident on the TFT 3. In this case, the reflective film 6 is formed ina region inside the gate lines 1 and the data lines 2 so as to suppressinfluences of the gate lines 1 and the data lines 2 and to cover thereflective film 6 completely with the transparent electrode film 5 lateron. As shown in FIG. 8, the reflective film 6 is formed so as not tooverlap the gate lines 1 or the data lines 2. Although this reflectivefilm 6 is usually made of aluminum (Al) or an aluminum (Al) alloy, thematerial of the reflective film 6 is not limited only to thesesubstances. It is possible to employ other metal as long as the metalhas high reflectance and compatibility to a liquid crystal process.

Next, as shown in FIG. 11A, an insulating film made of SiOx or the like,for instance, is deposited on the entire surface in accordance with theplasma CVD method or the like and selectively form a resist pattern.This insulating film is patterned and formed into the second passivationfilm 24. Exposed portions of the insulating film, the passivation film10, and the gate insulating film 9 are selectively etched with theresist pattern as the mask, and the source electrode 2 b is exposedthrough the contact hole 7. At the same time, more contact holes areformed on the G-D conversion portion and on the terminal portion.

Next, as shown in FIG. 11B, a transparent conductive film such as ITO isdeposited on the entire surface in accordance with the sputtering methodor the like, and the transparent electrode film 5 that covers the entiresurface of each pixel, a G-D conversion portion electrode 22, and aterminal electrode 23 are formed at the same time by use of a resistpattern. Here, in order to prevent an electrolytic corrosion reaction ofthe reflective film 6 located below, the transparent electrode film 5 isformed so as to cover the entire surface of the reflective film 6.Particularly, the transparent electrode film 5 is formed such that itsedges protrude above the gate lines 1 and the data line 2. By applyingthe laminated structure and the layout structure of the reflective film6 and the transparent electrode film 5 as described above, it ispossible to prevent the reflective film 6 from contacting the developer.

In this embodiment, the second passivation film 24 is formed between thereflective film 6 and the transparent electrode film 5. As thereflective film 6 is electrically floating, there is a concern ofvariation in the electric potential of the reflective film 6attributable to the gate voltage or the like to be applied to the TFT 3.However, by forming the concavo-convex film 11 on the TFT 3 as describedpreviously, it is possible to secure the distance between the TFT 3 andthe reflective film 6 with this concavo-convex film 11 and thereby torelieving the influence of the TFT 3 on the reflective film 6sufficiently. Thereafter, the alignment film 29 made of polyimide isformed on the transparent electrode film 5, thereby finishing theactive-matrix substrate 12.

Next, the counter substrate 16 is prepared by forming the color filter14, the black matrix (not shown), the counter electrode 15, thealignment film 29, and the like sequentially on the transparentinsulating substrate 13.

Then, the liquid crystal layer 17 is inserted between the two substrates12 and 16 and then the substrates are attached to each other.Furthermore, the retarders 20 a and 20 b and the polarizers 19 a and 19b are placed on both sides of the substrates. 12 and 16, respectively.Moreover, the backlight source 18 is located on the back side of thepolarizer 19 a placed on the active-matrix substrate 12. In this way,the semi-transmissive reflective LCD device is manufactured as shown inFIG. 9.

As described above, according to the semi-transmissive reflective LCDdevice and the manufacturing method thereof according to thisembodiment, it is possible to condense the light efficiently toward aviewer by use of the reflective film 6 formed on the concavo-convex film11 having the smaller tilt angle or the longer slope at the tiltedportion on the light incident side as similar to the first exemplaryembodiment. Therefore, it is possible to obtain a high reflectioncharacteristic with enhanced visibility. Moreover, upon formation of theconcavo-convex film 11, it is possible to form three regions havingdifferent exposure amounts at one session of exposure by use of thephotomask that includes the light-shielding region 31 a provided withthe pattern in the size equal to or larger than the resolution limit,the first transmissive region 31 b provided with the pattern in thesmaller size than the resolution limit, and the second transmissiveregion 31 c without patterns. In other words, since it is to 2.9 μm. Bysetting the film thickness of the concavo-convex film 11 approximatelyequal to 1.4 μm (=2.9 μm−1.5 μm), the cell gap dr in the reflectiveregion PXb is set an optimum value of about 1.5 μm. To realize thisstructure, the condition for coating the photosensitive acrylic resin isadjusted upon formation of the concavo-convex film 11 in the stepillustrated in FIG. 10B so as to achieve the film thickness of about 1.4μm, for example. Moreover, the exposure process may be conducted to formthe contact hole 7 in the photosensitive acrylic resin on the sourceelectrode 2 b and to remove the photosensitive acrylic resin in thetransmissive region PXa at the same time in the same manner. In thisway, the photosensitive acrylic resin in the transmissive region PXa isremoved in the subsequent development process. Thereafter, the stepssubstantially similar to those described above are carried out.Eventually, it is possible to manufacture the semi-transmissivereflective LCD device as shown in FIG. 12, which is compatible to thetwist angle of about 0° by setting the reflection cell gap dr in thereflective region approximately equal to 1.5 μm and the transmissioncell gap df in the transmissive region approximately equal to 2.9 μm.

Although this embodiment describes the method of manufacturing thesemi-transmissive reflective LCD device, it is also possible tomanufacture a reflective LCD device by forming the pixel region PXentirely as the reflective region PXb. Moreover, this embodimentdescribes the case of applying the reflector explained in the firstexemplary embodiment to the LCD device. However, the present inventionis not limited only to this embodiment. It is to be noted that thepresent invention is also applicable to other reflectors for variouspurposes which include a function to enhance optical reflectance in acertain direction.

Although the preferred embodiments of the invention has been describedwith reference to the drawings, it will be obvious to those skilled inthe art that various changes or modifications may be made withoutdeparting from the true scope of the invention. For example, instead ofplacing the color filter 14 on the counter substrate 16, it is possibleto place the color filter 14 on the active-matrix substrate 12. When theLCD device is of a black-and-white type, it is possible to omit thecolor filter.

The above-described embodiment provides the LCD device including theelectrically floating reflective film 11 on the surface of theconcavo-convex film 11. Instead, it is also possible to apply thepresent invention to a reflective or semi-transmissive reflective LCDdevice in which the reflector itself constitutes a reflective pixelelectrode that is electrically connected to the source electrode 2 b ofthe TFT 3. That is, it is also possible to form the reflective pixelelectrode by connecting the reflector directly to the source electrode 2b of the TFT 3. Alternatively, it is also possible to form a reflectivepixel electrode by allowing the reflector to contact the transparentelectrode film 5 while connecting the transparent electrode film 5directly to the source electrode 2 b of the TFT 3. No matter whether thesubject is the electrically floating reflective film 6 or the reflectivepixel electrode, it is possible to reflect the incident lightefficiently toward a view and thereby to obtain a bright reflectioncharacteristic by forming the subject on the concavo-convex film 11 ofthis embodiment.

1. A reflector for reflecting incident light from outside, comprising:an insulating film formed on a substrate and including a plurality ofconcavities and convexities; and a metal film formed on the insulatingfilm, wherein convex portions constituting the plurality of concavitiesand convexities are formed into shapes in which the positions of peakportions in the entire convex portions are tilted in one direction whenviewed from a direction of a normal line of the substrate.
 2. Thereflector according to claim 1, wherein the concavities and theconvexities are formed by arranging a pattern including any of polygons,circles and ellipses in each of which any of the convex portion and theconcave portion is formed in at least one side thereof, or formed byarranging a pattern including any of wavy lines and winding lines alongeach of which any of the convex portion and the concave portion isformed.
 3. The reflector according to claim 1, wherein the insulatingfilm is a resin film.
 4. A reflector for reflecting incident light fromoutside, comprising: an insulating film formed on a substrate andincluding a plurality of concavities and convexities; and a metal filmformed on the insulating film, wherein a tilted portion between a peakportion of each of convex portions constituting the plurality ofconcavities and convexities and a concave portion around the convexportion has a tilt angle to a surface of the substrate, the tilt angleon a predetermined side being relatively smaller than the tilt angle onanother side.
 5. The reflector according to claim 4, wherein theconcavities and the convexities are formed by arranging a patternincluding any of polygons, circles and ellipses in each of which any ofthe convex portion and the concave portion is formed in at least oneside thereof, or formed by arranging a pattern including any of wavylines and winding lines along each of which any of the convex portionand the concave portion is formed.
 6. The reflector according to claim4, wherein the insulating film is a resin film.
 7. A reflector forreflecting incident light from outside, comprising: an insulating filmformed on a substrate and including a plurality of concavities andconvexities; and a metal film formed on the insulating film, wherein atilted portion between a peak portion of each of convex portionsconstituting the plurality of concavities and convexities and a concaveportion around the convex portion has a slope which is relatively longeron a predetermined side than a slope on another side.
 8. The reflectoraccording to claim 7, wherein the concavities and the convexities areformed by arranging a pattern including any of polygons, circles andellipses in each of which any of the convex portion and the concaveportion is formed in at least one side thereof, or formed by arranging apattern including any of wavy lines and winding lines along each ofwhich any of the convex portion and the concave portion is formed. 9.The reflector according to claim 7, wherein the insulating film is aresin film.
 10. A liquid crystal display device comprising a pair ofsubstrates and a liquid crystal layer interposed between the pair ofsubstrates, wherein a reflector according to claim 1 is formed on eitherone of the pair of substrates.
 11. A liquid crystal display devicecomprising a pair of substrates and a liquid crystal layer interposedbetween the pair of substrates, wherein a reflector according to claim 4is formed on either one of the pair of substrates.
 12. A liquid crystaldisplay device comprising a pair of substrates and a liquid crystallayer interposed between the pair of substrates, wherein a reflectoraccording to claim 7 is formed on either one of the pair of substrates.13. A method of manufacturing a reflector for reflecting incident lightfrom outside comprising the steps of: coating photosensitive resin on asubstrate; exposing the photosensitive resin by use of a photomaskincluding a light-shielding region where a piece of a pattern is formedin a size equal to or larger than a resolution limit, a firsttransmissive region where a piece of a pattern is formed in a sizesmaller than the resolution limit, and a second transmissive regionhaving higher optical transmittance than the first transmissive region;performing development of the photosensitive resin after the exposureand then forming three regions having different film thicknesses;subjecting the photosensitive resin to a heat treatment after thedevelopment; and forming a reflective film on the photosensitive resinafter the heat treatment.
 14. The method of manufacturing a reflectoraccording to claim 13, wherein the photomask comprises a pattern inwhich any of polygons, circles, and ellipses are arranged in a planedirection, sides of any of the polygons, circles, and ellipsesconstitute the light-shielding region, and the first transmissive regionis located adjacent to the light-shielding region.
 15. The method ofmanufacturing a reflector according to claim 13, wherein the photomaskcomprises a pattern in which any of wavy lines and winding lines arearranged in a plane direction, any of each of the wavy lines and of thewinding lines constitutes the light-shielding region, and the firsttransmissive region is located adjacent to the light-shielding region.16. The method of manufacturing a reflector according to claim 13,wherein the photomask comprises a pattern in which any of polygons,circles, and ellipses are arranged in a plane direction, a side of anyof each polygon, circle, and ellipse constitutes the second transmissiveregion, and the first transmissive region and the light-shielding regionare located adjacent to each other in areas surrounded by sides of anyof the polygons, circles, and ellipses.
 17. The method of manufacturinga reflector according to claim 13, wherein the photomask comprises apattern in which any of wavy lines and winding lines are arranged in aplane direction, any of each wavy line and winding line constitutes thesecond transmissive region, and the first transmissive region and thelight-shielding region are located adjacent to each other at portionsother than any of the wavy lines and winding lines.
 18. The method ofmanufacturing a reflector according to claim 13, wherein a piece size ofthe pattern is smaller than the resolution limit, and the pattern ischanged stepwise in the first transmissive region.
 19. The method ofmanufacturing a reflector according to claim 13, wherein alight-shielding pattern is not formed in the second transmissive region.